Dairy cows are susceptible to many diseases such as mastitis, pneumonia, metritis, retained placenta, dystocia, foot rot, and milk fever. Some of these diseases interfere with the cow's ability to produce milk and may require that the cow be isolated and not commercially milked until cured. Untreated, some of these diseases can lead to death. Because of this potential for economic loss, dairy farmers strive to maintain their dairy cows in a healthy state. Also, healthy cows produce more and better quality milk, thus, increasing the dairy farmer's profit. As a result the dairy farmer needs to periodically medicate sick animals to bring them back to health. It is a common and necessary practice to treat lactating dairy cows for a variety of diseases by medicating them with antibiotics such as penicillin, other beta lactams, sulfas, aminoglycosides, tetracyclines, and gentamicin sulfate. Intravenous, intramuscular, and oral administration is common. These antibiotics may also be directly infused into the udder (intramammmary) in order to treat mastitis which is the most common illness in milk cows. These drugs enter the treated cow's bloodstream and also appear in the milk of the treated cow.
Regulatory agencies require that milk be free of animal drug residues because, e.g., penicillin and sulfonamides can cause allergic reactions in sensitive people ranging from skin rashes to severe respiratory problems and anaphylactic shock. About 80% to about 90% of milk contaminated with antibiotics is contaminated with penicillin. Also, exposure to veterinary antibiotics in milk can negatively affect an individual's resistance to antibiotics made for humans and render them less, or totally, ineffective. In addition, some animal drug compounds are suspected carcinogens. For these reasons, plus the fact that consumers prefer to consume "natural" milk, i.e., free of added chemicals, current regulations require that all milk be tested for the presence of animal drugs prior to use.
Animal drugs are normally kept out of the milk sold to processors by isolating the treated cow and disposing of the milk from treated cows for the period of time specified by the drug manufacturer. In spite of these precautions, milk containing antibiotic residues is sometimes unknowingly acquired by milk processors. Some of the major reasons why contaminated milk finds it way to processors are: some cows retain drugs longer than the average isolation period recommended by drug manufacturers, treated cows are not marked or identified, sellers of recently treated cows do not advise the purchaser of the treatment, lack of communication between the individual responsible for treating the cow and the individual responsible for milking, treating the wrong cow, lack of training of treating and milking personnel, and administering multiple drugs in a single treatment. Most milk is purchased and delivered to the processor in bulk loads. Most bulk loads of milk contain multiple sources of milk. Should a dairy farmer accidentally or intentionally misuse a drug while treating a cow, the milk from even one improperly treated cow will contaminate his entire bulk shipment--which in turn will contaminate the entire bulk load to which it is added.
Currently milk containing antibiotics and other animal drug residues cannot be fed to humans or animals. At the present time, milk found to contain animal drugs cannot be reconditioned, blended or used for human consumption. The United States Food and Drug Administraion has stated that it is not aware of any currently acceptable process that can be used to eliminate drug residues in milk and recondition the milk for human consumption. (See Memorandum from the Chief of the Food and Drug Administration Milk Safety Branch dated Nov. 16, 1990 (FDA Policy regarding the disposition of raw milk that contains drug residue). The contaminated milk is generally disposed of by land spreading at zero value. When the processor must dispose of a bulk shipment containing some contaminated milk (because one of the multiple sources has contaminated the entire bulk shipment), the processor must still pay the dairy farmers supplying uncontaminated milk the full value for their milk. This causes the processor significant economic loss. In addition, at certain times of the year government environmental agencies will not permit land disposal of milk contaminated with antibiotics, thus, giving the processor limited, and expensive, disposal options such as storage, treatment at a municipal waste treatment plant, or incineration.
A means to remove the antibiotics is sought to recover the milk for some acceptable use and recover some or all of its economic value. Removal of these drugs will permit utilization of this milk by humans and animals. The need exists, therefore, for a method of removing antibiotics from milk.